contrib/bind-9.3/bin/dig/host.html

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  17 <!-- $Id: host.html,v 1.4.2.1.4.14 2006/06/29 13:02:30 marka Exp $ -->
  18 <html>
  19 <head>
  20 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
  21 <title>host</title>
  22 <meta name="generator" content="DocBook XSL Stylesheets V1.70.1">
  23 </head>
  24 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
  25 <a name="id2482688"></a><div class="titlepage"></div>
  26 <div class="refnamediv">
  27 <h2>Name</h2>
  28 <p>host &#8212; DNS lookup utility</p>
  29 </div>
  30 <div class="refsynopsisdiv">
  31 <h2>Synopsis</h2>
  32 <div class="cmdsynopsis"><p><code class="command">host</code>  [<code class="option">-aCdlnrTwv</code>] [<code class="option">-c <em class="replaceable"><code>class</code></em></code>] [<code class="option">-N <em class="replaceable"><code>ndots</code></em></code>] [<code class="option">-R <em class="replaceable"><code>number</code></em></code>] [<code class="option">-t <em class="replaceable"><code>type</code></em></code>] [<code class="option">-W <em class="replaceable"><code>wait</code></em></code>] [<code class="option">-4</code>] [<code class="option">-6</code>] {name} [server]</p></div>
  33 </div>
  34 <div class="refsect1" lang="en">
  35 <a name="id2549466"></a><h2>DESCRIPTION</h2>
  36 <p>
  37 <span><strong class="command">host</strong></span>
  38 is a simple utility for performing DNS lookups.
  39 It is normally used to convert names to IP addresses and vice versa.
  40 When no arguments or options are given,
  41 <span><strong class="command">host</strong></span>
  42 prints a short summary of its command line arguments and options.
  43 </p>
  44 <p>
  45 <em class="parameter"><code>name</code></em> is the domain name that is to be looked
  46 up.  It can also be a dotted-decimal IPv4 address or a colon-delimited
  47 IPv6 address, in which case <span><strong class="command">host</strong></span> will by default
  48 perform a reverse lookup for that address.
  49 <em class="parameter"><code>server</code></em> is an optional argument which is either
  50 the name or IP address of the name server that <span><strong class="command">host</strong></span>
  51 should query instead of the server or servers listed in
  52 <code class="filename">/etc/resolv.conf</code>.
  53 </p>
  54 <p>
  55 The <code class="option">-a</code> (all) option is equivalent to setting the
  56 <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
  57 a query of type ANY.
  58 </p>
  59 <p>
  60 When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
  61 will attempt to display the SOA records for zone
  62 <em class="parameter"><code>name</code></em> from all the listed authoritative name
  63 servers for that zone.  The list of name servers is defined by the NS
  64 records that are found for the zone.
  65 </p>
  66 <p>
  67 The <code class="option">-c</code> option instructs to make a DNS query of class
  68 <em class="parameter"><code>class</code></em>.  This can be used to lookup Hesiod or
  69 Chaosnet class resource records.  The default class is IN (Internet).
  70 </p>
  71 <p>
  72 Verbose output is generated by <span><strong class="command">host</strong></span> when the
  73 <code class="option">-d</code> or <code class="option">-v</code> option is used.  The two
  74 options are equivalent.  They have been provided for backwards
  75 compatibility.  In previous versions, the <code class="option">-d</code> option
  76 switched on debugging traces and <code class="option">-v</code> enabled verbose
  77 output.
  78 </p>
  79 <p>
  80 List mode is selected by the <code class="option">-l</code> option.  This makes
  81 <span><strong class="command">host</strong></span> perform a zone transfer for zone
  82 <em class="parameter"><code>name</code></em>.  Transfer the zone printing out the NS, PTR
  83 and address records (A/AAAA).  If combined with <code class="option">-a</code>
  84 all records will be printed.
  85 </p>
  86 <p>
  87 The <code class="option">-i</code>
  88 option specifies that reverse lookups of IPv6 addresses should
  89 use the IP6.INT domain as defined in RFC1886.
  90 The default is to use IP6.ARPA.
  91 </p>
  92 <p>
  93 The <code class="option">-N</code> option sets the number of dots that have to be
  94 in <em class="parameter"><code>name</code></em> for it to be considered absolute.  The
  95 default value is that defined using the ndots statement in
  96 <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots statement is
  97 present.  Names with fewer dots are interpreted as relative names and
  98 will be searched for in the domains listed in the <span class="type">search</span>
  99 or <span class="type">domain</span> directive in
 100 <code class="filename">/etc/resolv.conf</code>.
 101 </p>
 102 <p>
 103 The number of UDP retries for a lookup can be changed with the
 104 <code class="option">-R</code> option.  <em class="parameter"><code>number</code></em> indicates
 105 how many times <span><strong class="command">host</strong></span> will repeat a query that does
 106 not get answered.  The default number of retries is 1.  If
 107 <em class="parameter"><code>number</code></em> is negative or zero, the number of
 108 retries will default to 1.
 109 </p>
 110 <p>
 111 Non-recursive queries can be made via the <code class="option">-r</code> option.
 112 Setting this option clears the <span class="type">RD</span> &#8212; recursion
 113 desired &#8212; bit in the query which <span><strong class="command">host</strong></span> makes.
 114 This should mean that the name server receiving the query will not
 115 attempt to resolve <em class="parameter"><code>name</code></em>.  The
 116 <code class="option">-r</code> option enables <span><strong class="command">host</strong></span> to mimic
 117 the behaviour of a name server by making non-recursive queries and
 118 expecting to receive answers to those queries that are usually
 119 referrals to other name servers.
 120 </p>
 121 <p>
 122 By default <span><strong class="command">host</strong></span> uses UDP when making queries.  The
 123 <code class="option">-T</code> option makes it use a TCP connection when querying
 124 the name server.  TCP will be automatically selected for queries that
 125 require it, such as zone transfer (AXFR) requests.
 126 </p>
 127 <p>
 128 The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
 129 use IPv4 query transport.  The <code class="option">-6</code> option forces
 130 <span><strong class="command">host</strong></span> to only use IPv6 query transport.
 131 </p>
 132 <p>
 133 The <code class="option">-t</code> option is used to select the query type.
 134 <em class="parameter"><code>type</code></em> can be any recognised query type: CNAME,
 135 NS, SOA, SIG, KEY, AXFR, etc.  When no query type is specified,
 136 <span><strong class="command">host</strong></span> automatically selects an appropriate query
 137 type.  By default it looks for A records, but if the
 138 <code class="option">-C</code> option was given, queries will be made for SOA
 139 records, and if <em class="parameter"><code>name</code></em> is a dotted-decimal IPv4
 140 address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
 141 query for PTR records.  If a query type of IXFR is chosen the starting
 142 serial number can be specified by appending an equal followed by the
 143 starting serial number (e.g. -t IXFR=12345678).
 144 </p>
 145 <p>
 146 The time to wait for a reply can be controlled through the
 147 <code class="option">-W</code> and <code class="option">-w</code> options.  The
 148 <code class="option">-W</code> option makes <span><strong class="command">host</strong></span> wait for
 149 <em class="parameter"><code>wait</code></em> seconds.  If <em class="parameter"><code>wait</code></em>
 150 is less than one, the wait interval is set to one second.  When the
 151 <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span> will
 152 effectively wait forever for a reply.  The time to wait for a response
 153 will be set to the number of seconds given by the hardware's maximum
 154 value for an integer quantity.
 155 </p>
 156 </div>
 157 <div class="refsect1" lang="en">
 158 <a name="id2549874"></a><h2>FILES</h2>
 159 <p>
 160 <code class="filename">/etc/resolv.conf</code>
 161 </p>
 162 </div>
 163 <div class="refsect1" lang="en">
 164 <a name="id2549886"></a><h2>SEE ALSO</h2>
 165 <p>
 166 <span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
 167 <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
 168 </p>
 169 </div>
 170 </div></body>
 171 </html>